From: g_d_pusch_remove_underscores@xnet.com   
      
   Sander Vesik  writes:   
      
   > Henry Spencer  wrote:   
   >>   
   >> The latter.  If memory serves, even at SSME pressures, flame temperature   
   >> is limited more by dissociation of the reaction products than by energy   
   >> available.  To put extra energy into the exhaust of a good rocket engine,   
   >> you need to use non-thermal means.  (Running an electromagnetic thruster   
   >> on the exhaust of a NERVA, with the reactor supplying the power, has been   
   >> suggested.)   
   >   
   > Would "microwaving" the output of a LOX/LH2 engine work? After all, the   
   > exhaust is water, and you already have fast-spining turbopumps powered   
   > by gas turbines to which you only need to attach more stuff. Or is this a   
   > crackpot idea?   
      
   There are these two annoying things called the Fisrt and Second Laws of   
   Thermodynamics. The First Law implies that the energy for "microwaving"   
   the exhaust has to come from somewhere. Since the only source of energy   
   in a chemically fueled vehicle is the chemical fuel, running some of the   
   propellant through a gas-turbine generator takes propellant away from   
   the main engine, decreasing the amount of potential thrust-producing   
   reaction mass available, which cuts into the total impulse. Furthermore,   
   the Second Law of Thermodynamics guarantess that the amount of energy   
   re-injected into the jet by the "microwaving" process must _ALWAYS_ be   
   less than if you'd simply burned the propellant in the engine in the   
   first place. Hence, your proposal actually _hurst_ performance two ways,   
   unless you have some magic lightweight source of non-chemical energy   
   available to heat the propellant...   
      
      
   -- Gordon D. Pusch   
      
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